The rescale isn't sure yet. Some sources have posted that this was confirmed, whilst others have mentioned this might not be the case. Here a little quote from Tactical Command:

Slightly OT but BFG was commented on: apparently its years off (Tony C) and will be battlefleet heresy, not gothic. Andy again has said no scale has been decided on for BFG (of BFH rather!) But I think this is a way of shutting the guy up yelling about how GW are screwing over the loyal fans with scale change (yawn!)